File Upload

To create a file upload button, two elements are needed: a label or button and an input.


When we set the for attribute to the same value as the id of the input, we enable the input to be triggered by clicking on the label or button. We then hide the input.


After uploading the files, you will receive an IReadOnlyList<IBrowserFile> or IBrowserFile and you will need to manually handle the upload in HandleFilesChanged. Instead of using multiple to allow multiple files, you set T to IReadOnlyList<IBrowserFile>. Using IBrowserFile restricts the component to a single file.



API
Use any type of MudButton

Use a MudButton, a MudIconButton or a MudFab with the HtmlTag property set to "label" within the ButtonTemplate render fragment. Be sure to set the button's ID using the @context parameter.
A MudFileUpload can be Disabled and it will Disable its child button automatically.

0 Files:
<MudFileUpload T="IBrowserFile" FilesChanged="UploadFiles">
    <ButtonTemplate>
        <MudButton HtmlTag="label"
                   Variant="Variant.Filled"
                   Color="Color.Primary"
                   StartIcon="@Icons.Material.Filled.CloudUpload"
                   for="@context">
            Upload Files
        </MudButton>
    </ButtonTemplate>
</MudFileUpload>

<MudFileUpload T="IBrowserFile" FilesChanged="UploadFiles">
    <ButtonTemplate>
        <MudFab HtmlTag="label"
                Color="Color.Secondary"
                Icon="@Icons.Material.Filled.Image"
                Label="Load picture"
                for="@context" />
    </ButtonTemplate>
</MudFileUpload>

<MudFileUpload T="IBrowserFile" FilesChanged="UploadFiles">
    <ButtonTemplate>
        <MudFab HtmlTag="label"
                Color="Color.Success"
                Icon="@Icons.Material.Filled.AttachFile"
                for="@context" />
    </ButtonTemplate>
</MudFileUpload>

<MudFileUpload T="IBrowserFile" FilesChanged="UploadFiles">
    <ButtonTemplate>
        <MudIconButton HtmlTag="label"
                       Color="Color.Info"
                       Icon="@Icons.Material.Filled.PhotoCamera"
                       for="@context">
        </MudIconButton>
    </ButtonTemplate>
</MudFileUpload>

<MudFileUpload T="IBrowserFile" FilesChanged="UploadFiles" Disabled>
    <ButtonTemplate>
        <MudButton HtmlTag="label"
                   Variant="Variant.Filled"
                   Color="Color.Primary"
                   for="@context">
            Disabled Button
        </MudButton>
    </ButtonTemplate>
</MudFileUpload>

@if (files != null)
{
    <MudText Typo="@Typo.h6">@files.Count() File@(files.Count() == 1 ? "" : "s"):</MudText>
    <MudList>
        @foreach (var file in files)
        {
            <MudListItem Icon="@Icons.Material.Filled.AttachFile" @key="@file">
                @file.Name <code>@file.Size bytes</code>
            </MudListItem>
        }
    </MudList>
}

@code
{
    IList<IBrowserFile> files = new List<IBrowserFile>();
    private void UploadFiles(IBrowserFile file)
    {
        files.Add(file);
        //TODO upload the files to the server
    }
}
Multiple and Accept

Allow multiple files with T="IReadOnlyList<IBrowserFile>" or limit the valid file types with Accept. To upload more than 10 files, you must specify a MaximumFileCount. 

<MudFileUpload T="IReadOnlyList<IBrowserFile>" FilesChanged="UploadFiles">
    <ButtonTemplate>
        <MudButton HtmlTag="label"
                   Variant="Variant.Filled"
                   Color="Color.Primary"
                   StartIcon="@Icons.Material.Filled.CloudUpload"
                   for="@context">
            Multiple Files
        </MudButton>
    </ButtonTemplate>
</MudFileUpload>

<MudFileUpload T="IBrowserFile" Accept=".pdf" FilesChanged="UploadFiles2" MaximumFileCount="100">
    <ButtonTemplate>
        <MudButton HtmlTag="label"
                   Variant="Variant.Filled"
                   Color="Color.Primary"
                   StartIcon="@Icons.Material.Filled.CloudUpload"
                   for="@context">
            Only .pdf files
        </MudButton>
    </ButtonTemplate>
</MudFileUpload>

@if (files != null)
{
    <MudList>
        @foreach (var file in files)
        {
            <MudListItem Icon="@Icons.Material.Filled.AttachFile">
                @file.Name <code>@file.Size bytes</code>
            </MudListItem>
        }
    </MudList>
}

@code
{
    IList<IBrowserFile> files = new List<IBrowserFile>();
    private void UploadFiles(IReadOnlyList<IBrowserFile> files)
    {
        foreach (var file in files)
        {
            this.files.Add(file);
        }
        //TODO upload the files to the server
    }

    private void UploadFiles2(IBrowserFile file)
    {
        files.Add(file);
        //TODO upload the files to the server
    }
}
Form Validation

Use the For property to validate your files within a form, and bind your files to your model class using @bind-Files. You can then handle the file upload logic within your MudForm submit method. 

@using FluentValidation
@using Severity = MudBlazor.Severity;
@inject ISnackbar Snackbar

<MudCard>
    <MudForm Model="@model" @ref="@form" Validation="@(ValidationRules.ValidateValue)" ValidationDelay="0">
        <MudCardContent>
            <MudTextField @bind-Value="model.Name"
                          For="@(() => model.Name)"
                          Immediate="true"
                          Label="Name" />
            <MudFileUpload T="IBrowserFile" For="@(() => model.File)" @bind-Files="model.File" OnFilesChanged="UploadFiles" SuppressOnChangeWhenInvalid="SuppressOnChangeWhenInvalid">
                <ButtonTemplate>
                    <MudButton HtmlTag="label"
                               Variant="Variant.Filled"
                               Color="Color.Primary"
                               StartIcon="@Icons.Material.Filled.CloudUpload"
                               for="@context">
                        Upload Files
                    </MudButton>
                </ButtonTemplate>
            </MudFileUpload>
        </MudCardContent>
        <MudCardActions>
            <MudSwitch Color="Color.Primary" @bind-Checked="SuppressOnChangeWhenInvalid">Suppress OnChange When Invalid</MudSwitch>
            <MudButton Variant="Variant.Filled" Color="Color.Primary" Class="ml-auto" OnClick="@(async () => await Submit())">Submit</MudButton>
        </MudCardActions>
    </MudForm>
</MudCard>

@code
{
    private MudForm form;
    private FileModel model = new();
    private FileModelFluentValidator ValidationRules = new();
    private bool SuppressOnChangeWhenInvalid;

    private void UploadFiles(InputFileChangeEventArgs e)
    {
        //If SuppressOnChangeWhenInvalid is false, perform your validations here
        Snackbar.Configuration.PositionClass = Defaults.Classes.Position.TopCenter;
        Snackbar.Add($"This file has the extension {model.File.Name.Split(".").Last()}", Severity.Info);

        //TODO upload the files to the server
    }

    private async Task Submit()
    {
        await form.Validate();

        if (form.IsValid)
        {
            Snackbar.Add("Submited!");
        }
    }

    public class FileModel
    {
        public string Name { get; set; }
        public IBrowserFile File { get; set; }
    }

    /// <summary>
    /// A standard AbstractValidator which contains multiple rules and can be shared with the back end API
    /// </summary>
    /// <typeparam name="OrderModel"></typeparam>
    public class FileModelFluentValidator : AbstractValidator<FileModel>
    {
        public FileModelFluentValidator()
        {
            RuleFor(x => x.Name)
                .NotEmpty()
                .Length(1, 100);
            RuleFor(x => x.File)
            .NotEmpty();
            When(x => x.File != null, () =>
            {
                RuleFor(x => x.File.Size).LessThanOrEqualTo(10485760).WithMessage("The maximum file size is 10 MB");
            });
        }

        public Func<object, string, Task<IEnumerable<string>>> ValidateValue => async (model, propertyName) =>
        {
            var result = await ValidateAsync(ValidationContext<FileModel>.CreateWithOptions((FileModel)model, x => x.IncludeProperties(propertyName)));
            if (result.IsValid)
                return Array.Empty<string>();
            return result.Errors.Select(e => e.ErrorMessage);
        };
    }
}
Event Options

You can use either Files and FilesChanged or the OnFilesChanged callback. The former is better when used within a MudForm, and the latter is better for custom scenarios. When using OnFilesChanged, it will fire regardless of validation by default, but can be configured to only fire when valid using SuppressOnChangeWhenInvalid.

0 Files:
<MudFileUpload T="IBrowserFile" FilesChanged="UploadFiles">
    <ButtonTemplate>
        <MudButton HtmlTag="label"
                   Variant="Variant.Filled"
                   Color="Color.Primary"
                   StartIcon="@Icons.Material.Filled.CloudUpload"
                   for="@context">
            Upload using FileValueChanged
        </MudButton>
    </ButtonTemplate>
</MudFileUpload>

<MudFileUpload T="IBrowserFile" OnFilesChanged="UploadFiles">
    <ButtonTemplate>
        <MudButton HtmlTag="label"
                   Variant="Variant.Filled"
                   Color="Color.Primary"
                   StartIcon="@Icons.Material.Filled.CloudUpload"
                   for="@context">
            Upload using OnFilesChanged
        </MudButton>
    </ButtonTemplate>
</MudFileUpload>

@if (files != null)
{
    <MudText Typo="@Typo.h6">@files.Count() File@(files.Count() == 1 ? "" : "s"):</MudText>
    <MudList>
        @foreach (var file in files)
        {
            <MudListItem Icon="@Icons.Material.Filled.AttachFile" @key="@file">
                @file.Name <code>@file.Size bytes</code>
            </MudListItem>
        }
    </MudList>
}

@code
{
    IList<IBrowserFile> files = new List<IBrowserFile>();
    private void UploadFiles(IBrowserFile file)
    {
        files.Add(file);
        //TODO upload the files to the server
    }

    private void UploadFiles(InputFileChangeEventArgs args)
    {
        files.Add(args.File);
        //TODO upload the files to the server
    }
}
SelectedTemplate

You can use the SelectedTemplate RenderFragment to display the current files. Its @context parameter matches T.

No File

No Files

<MudFileUpload T="IBrowserFile">
    <ButtonTemplate>
        <MudButton HtmlTag="label"
                   Variant="Variant.Filled"
                   Color="Color.Primary"
                   for="@context">
            Single File
        </MudButton>
    </ButtonTemplate>
    <SelectedTemplate>
        @if (context != null)
        {
            <MudText>@context.Name</MudText>
        }
        else
        {
            <MudText>No File</MudText>
        }
    </SelectedTemplate>
</MudFileUpload>

<MudFileUpload T="IReadOnlyList<IBrowserFile>" Multiple>
    <ButtonTemplate>
        <MudButton HtmlTag="label"
                   Variant="Variant.Filled"
                   Color="Color.Secondary"
                   for="@context">
            Multiple Files
        </MudButton>
    </ButtonTemplate>
    <SelectedTemplate>
        @if (context != null)
        {
            @foreach (var file in context)
            {
                <MudText>@file.Name</MudText>
            }
        }
        else
        {
            <MudText>No Files</MudText>
        }
    </SelectedTemplate>
</MudFileUpload>
Drag and Drop Example

Using the example below, you can compose a drag-and-drop uploader.

Drag and drop files here or click
@inject ISnackbar Snackbar

<MudStack Style="width: 100%">
    <MudFileUpload T="IReadOnlyList<IBrowserFile>" OnFilesChanged="OnInputFileChanged" Hidden="false" Class="flex-1" InputClass="absolute mud-width-full mud-height-full overflow-hidden z-20" InputStyle="opacity:0"
                   @ondragenter="@SetDragClass" @ondragleave="@ClearDragClass" @ondragend="@ClearDragClass">
        <ButtonTemplate>
            <MudPaper Height="300px" Outlined="true" Class="@DragClass">
                <MudText Typo="Typo.h6">Drag and drop files here or click</MudText>
                @foreach (var file in fileNames)
                {
                    <MudChip Color="Color.Dark" Text="@file" />
                }
            </MudPaper>
        </ButtonTemplate>
    </MudFileUpload>
    <MudToolBar DisableGutters="true" Class="gap-4">
        <MudButton OnClick="Upload" Disabled="@(!fileNames.Any())" Color="Color.Primary" Variant="Variant.Filled">Upload</MudButton>
        <MudButton OnClick="Clear" Disabled="@(!fileNames.Any())" Color="Color.Error" Variant="Variant.Filled">Clear</MudButton>
    </MudToolBar>
</MudStack>

@code {
    private static string DefaultDragClass = "relative rounded-lg border-2 border-dashed pa-4 mt-4 mud-width-full mud-height-full z-10";
    private string DragClass = DefaultDragClass;
    private List<string> fileNames = new List<string>();

    private void OnInputFileChanged(InputFileChangeEventArgs e)
    {
        ClearDragClass();
        var files = e.GetMultipleFiles();
        foreach (var file in files)
        {
            fileNames.Add(file.Name);
        }
    }

    private async Task Clear()
    {
        fileNames.Clear();
        ClearDragClass();
        await Task.Delay(100);
    }
    private void Upload()
    {
        //Upload the files here
        Snackbar.Configuration.PositionClass = Defaults.Classes.Position.TopCenter;
        Snackbar.Add("TODO: Upload your files!", Severity.Normal);
    }

    private void SetDragClass()
    {
        DragClass = $"{DefaultDragClass} mud-border-primary";
    }

    private void ClearDragClass()
    {
        DragClass = DefaultDragClass;
    }
}
Field
Form
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